The use of communication cables which include a plurality of optical fibers is rapidly expanding. An optical fiber cable may comprise a plurality of glass fibers each of which is protected by at least one layer of a coating material. The optical fibers may be assembled into units in which the fibers are held together by binder ribbons to provide a core. In one manufacturer's line of cables, the core is enclosed by a plastic tube and a plastic jacket.
During the service life of an optical fiber cable, the cable may become damaged. This may occur, for example, through unintentional contact by various kinds of excavation equipment, by lightning or by repeated attacks by animals such as gophers. Such damage may be partial, in which case one or several optical fibers may be interrupted, or the damage may be total, such as a complete cable cut, for example.
In any case, it becomes necessary to restore service as quickly as possible. This may be done through an expedited temporary arrangement while more work is under way to replace the damaged cable with an equivalent or enhanced system.
A temporary arrangement must be one which is easily installed and which is low in cost. Elements of the arrangement must be capable of being packaged in a carrying case which is portable and desirably, in one which may be carried by an individual from a vehicle to a field location at which a disruption to service has occurred.
Whatever the structure of the damaged cable, there must be provisions for connecting, such as by splicing, transmission media of the cable on each side of the damage location to corresponding transmission media of a restoration cable which is used to bridge around the damage location. It is conventional to use a closure, within which all conductors are connected, wrapped and stored and protected environmentally.
During the connection of metallic conductors, it is customary to bend sharply the conductors, to provide access to other connections. The physical nature of glass optical fibers forecloses the adoption of connectorization techniques which are used with metallic conductors within a closure. Because of their small size and relative fragility, special considerations must be given to the handling of optical fibers in closures. Transmission capabilities may be impaired if an optical fiber is bent beyond an allowable bending radius, the point at which light no longer is totally contained in the core of the fiber. Furthermore, expected lives of the fibers will be reduced if bent to less than the minimum bending radius.
In the prior art, fiber slack normally has been provided adjacent to connective arrangements. When splicing optical fibers by mechanical means or by fusion, it becomes necessary to provide enough slack fiber so that the fiber can be pulled out of a closure and positioned in apparatus for the preparation of fiber ends and the joining together of the ends.
As might be expected, fiber closures are available in the prior art. Some of these prior art closures have shortcomings insofar as being used in a temporary restoration arrangement. See U.S. Pat. No. 4,820,007 which issued on Apr. 11, 1989 in the names of R. R. Ross and I. Vedejs. In it, a splice tray includes provisions on one side for holding optical fiber splices and metallic conductor splices on an opposite side. An electrical bonding and gripping assembly is adapted to be mounted on the splice tray. The closure also includes mating cover portions which are moved into engagement with each other to enclose the tray. Also, a waterblocking encapsulant may be introduced into the closure.
The prior art also includes an emergency restoration system which includes a self-contained portable system that is capable of being stored in a craftsperson's vehicle and carried in a handy carrying case to a cable damage location. One portion of a damaged optical fiber cable is inserted into one splice case and optical fibers of the cable are terminated in splicing devices therein. Another portion of the damaged cable on an opposite side of the damage location is terminated in another splice case. Portions of a temporary cable which is coiled adjacent an outer rim of the carrying case are uncoiled to span the damage location. Ends of the temporary cable are terminated by corresponding ones of the splicing devices in each splice case at each end of the temporary run. The temporary cable has an outer diameter of about 0.5 inch.
What is needed and what seemingly is not available in the prior art is a restoration kit for communications cable which kit is packaged in a carrying case with the weight of the kit and the case being less than about fifty pounds. The sought-after kit should be relatively inexpensive and should be capable of being deployed rapidly with easy payout of a restoration cable to restore service as quickly as possible after an outage.